A potent peptidomimetic inhibitor of botulinum neurotoxin serotype A has a very different conformation than SNAP-25 substrate.
Botulinum neurotoxin serotype A is the most lethal of all known toxins. Here, we report the crystal structure, along with SAR data, of the zinc metalloprotease domain of BoNT/A bound to a potent peptidomimetic inhibitor (K(i)=41 nM) that resembles the local sequence of the SNAP-25 substrate. Surprisingly, the inhibitor adopts a helical conformation around the cleavage site, in contrast to the extended conformation of the native substrate. The backbone of the inhibitor's P1 residue displaces the putative catalytic water molecule and concomitantly interacts with the "proton shuttle" E224. This mechanism of inhibition is aided by residue contacts in the conserved S1' pocket of the substrate binding cleft and by the induction of new hydrophobic pockets, which are not present in the apo form, especially for the P2' residue of the inhibitor. Our inhibitor is specific for BoNT/A as it does not inhibit other BoNT serotypes or thermolysin.
Zuniga
Jorge E
JE
Howard Hughes Medical Institute and Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA.
Schmidt
James J
JJ
Fenn
Timothy
T
Burnett
James C
JC
Araç
Demet
D
Gussio
Rick
R
Stafford
Robert G
RG
Badie
Shirin S
SS
Bavari
Sina
S
Brunger
Axel T
AT
D000595:Amino Acid Sequence; D001665:Binding Sites; D032701:Biomimetics; D019274:Botulinum Toxins, Type A / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D013379:Substrate Specificity; D050825:Synaptosomal-Associated Protein 25 / Q000737:chemistry* / Q000378:metabolism
D010446:Peptide Fragments; D050825:Synaptosomal-Associated Protein 25; D019274:Botulinum Toxins, Type A